Lots of U.S. food labels boast an absence of GMOs, but not many do the opposite. (Photo: Robyn Beck/AFP/Getty Images)

"The scientific community has spoken with one voice," U.S. Rep. Mike Pompeo, R-Kansas, recently told reporters while explaining a bill he'd introduced. He couldn't have meant the 97 percent scientific consensus about climate change, considering he co-sponsored a 2011 bill to exclude carbon dioxide and methane as pollutants under the Clean Air Act. So which singular scientific voice did he mean?

The one that says genetically modified organisms, or GMOs, are safe to eat. Pompeo's bill would uproot a recent crop of state-level efforts — including bills passed in Vermont, Connecticut and Maine — to require labels on foods that contain GMOs. Lots of products already carry "non-GMO" labels, but since up to 70 percent of U.S. food does contain GMOs, many consumer advocates want more transparency. GMO supporters, meanwhile, say labels would needlessly scare shoppers.

So who's right? Do scientists really agree genetically modified food is harmless? And if so, would a "GMO" label really make food seem scary? Let's wade a little deeper into the weeds to find out.

In 2013, 90 percent of all corn planted in the U.S. was genetically modified. (Photo: Shutterstock)

Sticker shock

Science does indicate GMOs are safe to eat, although the nature of its certainty inherently differs from the certainty of man-made climate change, despite occasional comparisons. (It's a lack of known risks vs. a known danger.) While there are valid environmental issues with GMOs, and with the industrial monocultures they encourage, any fears about human health are not well-supported by research.

Still, there has been enough uncertainty to prompt labeling laws in 64 other countries — and now in several U.S. states, too. After California and Washington voters rejected GMO-labeling initiatives in 2012, three states have passed labeling laws of some kind in 2013 and 2014 (a fourth was defeated in New Hampshire). Connecticut's and Maine's laws feature a "trigger," meaning they won't take effect until a certain number of other states pass similar laws, but Vermont's is written to stand alone.

"There is a lack of consensus regarding the validity of the research and science surrounding the safety of genetically engineered foods, as indicated by the fact that there are peer-reviewed studies published in international scientific literature showing negative, neutral, and positive health results," states the text of Vermont's bill, which Gov. Peter Shumlin signed into law on May 8. It's scheduled to take effect on July 1, 2016, but only if it can withstand an expected barrage of lawsuits.

Vermont could thus become a key battleground in the GMO-labeling debate. State leaders are already bracing for legal challenges to the law's constitutionality, and they're likely keeping an eye on Pompeo's bill, too. But why is there so much pushback against state-level efforts to simply label GMOs — especially among Republicans like Pompeo, who often favor robust states' rights? (To be fair, Pompeo's bill was co-sponsored by two Democrats as well as two fellow Republicans.)

"We've got a number of states that are attempting to put together a patchwork quilt of food labeling requirements with respect to [GMOs]," Pompeo told Reuters in April. "That makes it enormously difficult to operate a food system. Some of the campaigns in some of these states aren't really to inform consumers but rather aimed at scaring them. What this bill attempts to do is set a standard."

Preventing a patchwork may be sensible, but it doesn't preclude labeling GMOs. In fact, there's reason to believe GMO labels could have the opposite effect foretold by critics, at least in the long run. That's because labels — depending on their language, design and placement — have the potential to erode GMOs' stigma by demystifying them, reassuring shoppers their food has nothing to hide.

Genetically modified corn and soybeans are already widely used in U.S. processed foods. (Photo: Lyza/Flickr)

A seedy underbelly

Most Americans eat GMOs at some point. They've been widely grown on U.S. farms since the 1990s, and they're now the norm for many crops, especially those used in processed foods. Ninety percent of U.S. corn planted in 2013 was genetically modified, for example, as were 93 percent of U.S. soybeans.

But most Americans also want to end GMOs' culture of secrecy. In a national survey last year, more than 90 percent of respondents said GMOs should be identified in food. And that's not necessarily because they want to avoid them: Nearly half the respondents said they realize most processed foods in the U.S. already contain GMOs. Transparency and consumer choice carry a lot of weight in American culture, and they're also fairly universal values. Risk-perception research has long shown that people are typically less frightened by something if it seems unmysterious and controllable.

By resisting labels, GMO advocates may risk ceding the moral high ground — transparency — to foods that boast their lack of GMOs. When some food labels say "non-GMO" and others conspicuously ignore the subject, it might make the latter seem less trustworthy to shoppers. A skull-and-crossbones "warning label" obviously wouldn't help, but since there's no evidence to support such a message, it's much more likely the U.S. would label GMOs like other countries already do: blandly.

"GMO labels around the world are almost exclusively ingredient labels," author and GMO supporter Ramez Naam wrote for Discover magazine last year. "Those are the sorts of labels that can be agreed on now if the agricultural and biotech industries drive labeling or at least come to the table."

The idea that labels might improve GMOs' public image isn't new, but it has been getting more attention lately. "[P]eople judge voluntary, controllable actions as much less risky than those that are involuntary and out of their control," Grist's Nathanael Johnson wrote last year, citing a famous 1987 study on risk perception. "Similarly, people see the unknown as much more risky than the known. Genetically engineered foods are, for most people, both unknown and uncontrollable." Bryan Walsh of Time magazine echoed that argument when covering Pompeo's bill last month. "By passing a law that would preemptively ban any attempt to require labeling," he wrote, "GMO defenders are playing into the hands of their opponents, making bioengineering feel far more risky than it really is."

In countries that already require GMO labels, research reveals little effect on consumer behavior. Nonetheless, many pro-GMO scientists and scientific groups remain wary of labeling laws in the U.S. The Council for Agricultural Science and Technology, for one, recently warned in a report that "process-based food labeling is a very complex topic with nuanced marketing, economic and trade implications depending upon how the labeling laws are written and how the market responds."

GMOs have yet to cause any known health problems in humans, and common critiques are often based on faulty assumptions or misunderstandings. That's not to say GMOs are free of complications and uncertainty, but the evidence indicates they're not a danger to people who eat them.

Most major scientific organizations worldwide have vouched for GMOs, including the American Association for the Advancement of Science, the U.S. National Academy of Sciences, the U.K. Royal Society of Medicine, the French Academy of Science, and the Union of German Academies of Sciences and Humanities, among others. The World Health Organization (WHO) also says genetically modified food is safe so far, but it adds a caveat that ongoing scrutiny is warranted.

"GM foods currently available on the international market have passed risk assessments and are not likely to present risks for human health," the WHO states. "In addition, no effects on human health have been shown as a result of the consumption of such foods by the general population in the countries where they have been approved." At the same time, however, the WHO retains a note of caution about blanket enthusiasm for GMOs. "Different GM organisms include different genes inserted in different ways. This means that individual GM foods and their safety should be assessed on a case-by-case basis and that it is not possible to make general statements on the safety of all GM foods."

One high-profile study in 2012 did link GMOs to health problems in rats, but it was later retracted. Led by French researcher Gilles-Éric Séralini, the study reported rats given GM corn and pesticides made by biotech firm Monsanto developed "severe adverse health effects including mammary tumors and kidney and liver damage, leading to premature death." Critics quickly pointed out faults in the study's design, including a small sample size and the use of a tumor-prone strain of lab rat. (In his defense, Séralini has noted Monsanto used the same type of rats in its own studies on GM corn.)

"Ultimately, the results presented (while not incorrect) are inconclusive, and therefore do not reach the threshold of publication," journal publisher Elsevier explained in a statement about its retraction.

Health concerns persist, though, mainly related to indirect effects from the cultivation of GMOs. Since many GM crops are engineered to tolerate herbicides, some scientists warn the resulting increase in herbicide use to kill weeds could pose undiscovered human health risks. On the other hand, certain insect-resistant GM crops can also reduce the need for harmful insecticides.

Environmental effects of GMOs are similarly complex. Less insecticide is usually good for ecosystems — particularly pollinating insects like bees — but more herbicide can be trouble. It has been linked to monarch butterfly declines, for example, and along with the risk of genes fleeing GM crops into nature, it can give rise to herbicide-resistant "superweeds." Despite such pitfalls, though, scientists generally don't consider GMOs on their own a major environmental problem.

"[Genetically engineered] crops have had fewer adverse effects on the environment than non-GE crops produced conventionally," the U.S. National Research Council concluded in a 2010 report, although it added that "excessive reliance on a single technology combined with a lack of diverse farming practices could undermine the economic and environmental gains from these GE crops."

Regardless of how Pompeo's bill fares — the website GovTrack gives it a 4 percent chance of being enacted — or what happens in Vermont, the well-worn debate over GMO labels is unlikely to be settled soon. And in the meantime, given growing threats to food security and ecological stability from wildly changing climates, maybe the spotlight can shift to an even more urgent scientific chorus.

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